how big is the universe?

I'm having trouble understanding just how big the universe is.

Many people I talk to seem to think (assuming, for example, that the
universe is 13 billion years old)- that it's 13 billion light years in
radius- that we can almost see back to the edge- of course there is no edge
and that's all about lookback time and the "observable universe", not
current reality and distances.

Assuming that Guth's theory of inflation is more or less true- I vaguely
remember reading in some "popular" astronomy book that the universe inflated
to a size much bigger than the observable universe- so that the O.U. is a
tiny little part of the total universe. If this is the case, how could we
know how big it is? And, I've seen some recent cosmology writing implying
that it is infinite. I can understand the suggestion that if space will
continue to get bigger forever- that it is "open"- but I can't equate open
with infinite. I think when some astronomers say infinite, they don't mean
to imply infinite as we non scientists think of it.

Anyways, I find this all very fascinating. It's tough enough to imagine that
the universe may be 10-15 billion light years to the "edge"- but to ponder
that this observable universe may only be a tiny part of a much bigger
inflated universe really pushes me over the edge. <G>

But, I'm rambling- if the universe is much bigger than the observable
universe- how could we ever know how big it is? And, when astronomers try to
determine the total mass- do they mean the total mass of the observable
universe or the total universe, and does it make a difference?

One last bit of rambling- I have this crazy idea that if we can ever figure
out what dark matter and dark energy is- not only will all of that contain a
vast amount of information- similar to the way that electromagnetic energy
contains info- but that such discoveries will cause a quantum level advance
in the physical sciences- so important that it will be a milestone in human
evolution.

JZ